Average Speed

            It was a long drive. I drove 60 kilometres at 30 kilometres per hour and then an additional 60 kilometres at 50 kilometres per hour. Compute my average speed over the 120 kilometres.

Answer:   Time required for the first sixty miles                            : 120 minutes

                Time required for the second sixty miles                        :72 minutes

                Total time required                                                       : 192 minutes

I travelled 120 miles in 192 minutes. Therefore the average speed n miles per hour was   : 60 x 120 / 192   =37 ½